Change .pxd files to reflect changed rocksdb API's

rocksdb/backup.pxd

@@ -28,7 +28,6 @@ cdef extern from "utilities/backupable_db.h" namespace "rocksdb":
         void GetBackupInfo(vector[BackupInfo]*) nogil except+
         Status RestoreDBFromBackup(BackupID, string&, string&) nogil except+
         Status RestoreDBFromLatestBackup(string&, string&) nogil except+
-        void DeleteBackupsNewerThan(uint64_t) nogil except+
 
     cdef BackupEngine* NewBackupEngine "rocksdb::BackupEngine::NewBackupEngine"(
             Env*,

rocksdb/db.pxd

@@ -17,8 +17,8 @@ cdef extern from "rocksdb/write_batch.h" namespace "rocksdb":
         void Delete(const Slice&) nogil except+
         void PutLogData(const Slice&) nogil except+
         void Clear() nogil except+
-        string Data() nogil except+
-        int Count() nogil const
+        const string& Data() nogil except+
+        int Count() nogil except+
 
 cdef extern from "rocksdb/db.h" namespace "rocksdb":
     ctypedef uint64_t SequenceNumber